The high activity of polyol dehydrogenase (PD) in human lenses but not in those from animals, leads to serious questions about the direction and control of flux through the sorbitol pathway in various lenses; and about their responses to aldose reductase (AR) inhibitors such as those currently proposed for prevention of cataract in human diabetics. In human lenses, the apparent ability of PD to produce sorbitol from fructose is 80 times that of AR to produce sorbitol from glucose. The proposed study is directed toward a critical comparison of lenses from three species: rat (high AR, low PD), calf (moderate AR and PD), and man (low AR, high PD). Intact lenses in vitro will be used in order to preserve intra- and intercellular compartmentation and other factors such as nucleotide ratios. The temporal sequence of labelling of sorbitol and fructose from 14C-glucose will be studied under conditions known to result in increased, decreased or unchanged levels of total sorbitol, in the presence of AR inhibitors, and in diabetic lenses. The entry and metabolism of 14C-sorbitol and 14C-frustose into the various intact lenses will be evaluated. Secondly, the modes by which labelled sorbitol and fructose are removed from various lenses will be investigated under various physiological conditions as noted above. These projects rely on the accurate and reliable separation of labelled compounds by high-pressure liquid chromatography (HPLC). Calculation of the changes in specific radioactivity of individual compounds with time should allow evaluation of the sequence of reactions, the turnover capacity of the enzymes involved and the presence of pools with different turnover rates. Such data produce a more dynamic picture of differences in the operation of the sorbitol pathway in intact human and animal lenses under several physiological conditions.